Alright, everyone knows that securing at least one hive is vital to a win, and securing two is almost a sure win. So here is how you can do it and hold onto them successfully. Note: I tried this in a public server 10v10 3 times and it worked each time, but it might not work as well in a smaller game.
To get started, quickly build 1 or 2 spawn portals depending on how many people are in the game, a turret factory, and 3 turrets (no armory). Drop your men a few ammo packs because of the lack of ammo. Tell your men to wait for the skulk rush. If it doesnt come, send them to the middle hive (it should be in between the other two hives, for example computer core on ns_eclipse). Tell them to ignore any resource points on the way. Once you get to the hive, drop all the things you would put in your main base, because this will become your primary base. It makes more sense to make the middle hive your main base because they don't know it's your main base, they need to destroy it to get that hive, and it's closer to the other important places in the map. Send one man back to the original base to build another phase gate there. Recycle those spawn portals as well. The rest of your team should be on there way to the unoccupied hive. Fill it up with turrets, but you don't need as many because the aliens will most likely be attacking the middle hive. Also drop a phase gate. You now control two hives, the more important one being your main base, and they are left with skulks and lerks to try to take out your main base, which isn't going to happen. You control the game, so take all resource points on the map except the one in their original hive. At this time, you should be teching up as well. When you finally send in your heavy armored HMG toting marines, taking the last hive won't even be a challenge against resource starved level 1 aliens.
Get off my plane.